Energy useage/cost for average 1930s 3 bed semi?

[David]

I know, I know, piece of string etc.

A distantly related family member has had a "green energy upgrade" free of
charge from the local council.
It consists of solar panels, a hybrid system of air source heat pump and
gas boiler.
She is now struggling to pay the energy bills.
Reportedly £350 a month, but further information being sought.
Also trying to find out what the bills were prior to the "free" upgrade.

We have a (modified) 1930s 3 bed semi with good insulation (especially
after the extension), good solar gain, gas heating and hob, electric
cooker and microwave.

Our annual predicted bill this month is just over £2,500.
Just over £300 for the coldest months of the year, but considerably less
in the summer.

I am thinking that solar panels and an air source heat pump should reduce
overall running costs.
However it is possible that a poor installation would actually increase
annual costs.
In which case the installation would not be appropriate.

I am now asking if anyone has an "average" 1930s 3 bed semi, and if so
what the energy bills look like over the year.
Just for a comparison, to see if the costs in her case are abnormally high.

If her bills have gone up significantly after a "free" installation then
that opens a whole can of worms.

Cheers


Dave R

[Andy Burns]

Post by David
She is now struggling to pay the energy bills.
Reportedly £350 a month

Is that a disguised loan repayment for the 'free' system?

[David]

Post by Andy Burns

Post by David
She is now struggling to pay the energy bills.
Reportedly £350 a month

Is that a disguised loan repayment for the 'free' system?

As far as I know there are no concealed repayments.
I did ask the question, having a nasty suspicious mind.

At the moment just trying to establish an expected baseline cost for a gas
central heating house.

Cheers



Dave R

[Andrew]

Post by Andy Burns

Post by David
She is now struggling to pay the energy bills.
Reportedly £350 a month

Is that a disguised loan repayment for the 'free' system?

And why a heat pump *and* a gas boiler. This sounds a bit
odd.
Are we sure it isn't some sort of heat recovery system to
reduce condensation ?

[SteveW]

Post by Andrew

Post by Andy Burns

Post by David
She is now struggling to pay the energy bills.
Reportedly £350 a month

Is that a disguised loan repayment for the 'free' system?

And why a heat pump *and* a gas boiler. This sounds a bit
odd.
Are we sure it isn't some sort of heat recovery system to
reduce condensation ?

A gas boiler can still be used to give rapid warm-up of a building, that
a heat-pump may take a long period to get up to temperature. It can also
help on the coldest days, if necessary. It can provide almost unlimited
hot water.

[Andrew]

Post by SteveW

Post by Andrew

Post by Andy Burns

Post by David
She is now struggling to pay the energy bills.
Reportedly £350 a month

Is that a disguised loan repayment for the 'free' system?

And why a heat pump *and* a gas boiler. This sounds a bit
odd.
Are we sure it isn't some sort of heat recovery system to
reduce condensation ?

A gas boiler can still be used to give rapid warm-up of a building, that
a heat-pump may take a long period to get up to temperature. It can also
help on the coldest days, if necessary. It can provide almost unlimited
hot water.

Unlimited hot water for what ??

[SteveW]

Post by Andrew

Post by SteveW

Post by Andrew

Post by Andy Burns

Post by David
She is now struggling to pay the energy bills.
Reportedly £350 a month

Is that a disguised loan repayment for the 'free' system?

And why a heat pump *and* a gas boiler. This sounds a bit
odd.
Are we sure it isn't some sort of heat recovery system to
reduce condensation ?

A gas boiler can still be used to give rapid warm-up of a building,
that a heat-pump may take a long period to get up to temperature. It
can also help on the coldest days, if necessary. It can provide almost
unlimited hot water.

Unlimited hot water for what ??

Well, with a family of five, we use lots of hot water. The 40 gallon
tank can need a boost and a gas boiler does that rapidly. A bigger tank
is not an option, as it'd be in the way.

[SH]

Post by David
I know, I know, piece of string etc.
A distantly related family member has had a "green energy upgrade" free of
charge from the local council.
It consists of solar panels, a hybrid system of air source heat pump and
gas boiler.
She is now struggling to pay the energy bills.
Reportedly £350 a month, but further information being sought.
Also trying to find out what the bills were prior to the "free" upgrade.
We have a (modified) 1930s 3 bed semi with good insulation (especially
after the extension), good solar gain, gas heating and hob, electric
cooker and microwave.
Our annual predicted bill this month is just over £2,500.
Just over £300 for the coldest months of the year, but considerably less
in the summer.
I am thinking that solar panels and an air source heat pump should reduce
overall running costs.
However it is possible that a poor installation would actually increase
annual costs.
In which case the installation would not be appropriate.
I am now asking if anyone has an "average" 1930s 3 bed semi, and if so
what the energy bills look like over the year.
Just for a comparison, to see if the costs in her case are abnormally high.
If her bills have gone up significantly after a "free" installation then
that opens a whole can of worms.
Cheers
Dave R

switching from a gas fired heating & hot water system to an air source
heat pump actually worsens your EPC rating and as electricity is almost
4 x the cost of gas for the same amount of energy, your energy bills
will be higher.....

[Andy Burns]

as electricity is almost 4 x the cost of gas for the same amount of
energy, your energy bills will be higher.....

You're not allowing anything for the CoP of the heatpump?

[alan_m]

Post by Andy Burns

as electricity is almost 4 x the cost of gas for the same amount of
energy, your energy bills will be higher.....

You're not allowing anything for the CoP of the heatpump?

Or that a gas boiler may be running at 80%. or less, efficiency.

[RJH]

Post by alan_m

Post by Andy Burns

as electricity is almost 4 x the cost of gas for the same amount of
energy, your energy bills will be higher.....

You're not allowing anything for the CoP of the heatpump?

Or that a gas boiler may be running at 80%. or less, efficiency.

Or any uprated insulation (etc.) you'd hope accompanied the ASHP installation.

[Jeff Layman]

Post by alan_m

Post by Andy Burns

as electricity is almost 4 x the cost of gas for the same amount of
energy, your energy bills will be higher.....

You're not allowing anything for the CoP of the heatpump?

Or that a gas boiler may be running at 80%. or less, efficiency.

Only if it's old. Modern condensing gas boilers are around 94%.

[alan_m]

Post by Jeff Layman

Post by alan_m

Post by Andy Burns

as electricity is almost 4 x the cost of gas for the same amount of
energy, your energy bills will be higher.....

You're not allowing anything for the CoP of the heatpump?

Or that a gas boiler may be running at 80%. or less, efficiency.

Only if it's old. Modern condensing gas boilers are around 94%.

To get that figure you also have to improve the insulation and up-size
your radiators in the same way as you have to do with a ASHP. The 95%
figures are obtained with low flow/return temperatures and not the
60/70C that is commonplace in older central heating systems. In addition
you would probably have to install much better controls, and that
includes better than some of the popular smart thermostats or wireless
controllers.

[Alan Lee]

Post by Jeff Layman

Post by alan_m
Or that a gas boiler may be running at 80%. or less, efficiency.

Only if it's old. Modern condensing gas boilers are around 94%.

Unfortunately, they arent. That is the tested figure, in ideal
conditions, with a new boiler.
Once cycling of an oversized boiler is taken into account (90%+ of UK
boilers are oversized), most boilers struggle to get to 90%. Newer
modulating boilers help, and bring up efficincy gains, but unless the
system is designed for that boiler, they will never reach the claimed
efficieny figures quoted by the Manufacturers.

[Andrew]

Post by alan_m

Post by Andy Burns

as electricity is almost 4 x the cost of gas for the same amount of
energy, your energy bills will be higher.....

You're not allowing anything for the CoP of the heatpump?

Or that a gas boiler may be running at 80%. or less, efficiency.

But little or no gas is lost between Milford Haven or Norway
and the end user (and if any was Thansco would be on the
case PDQ), whereas quite a lot of electricity is 'lost'
between generator and end-user because of heat etc

OTOH, the residual heat from the gas boiler is within the
thermal envelope, whereas the heat from the outside compressor
and fan motor of a heat pump, really is lost to the outside air.

[The Natural Philosopher]

Post by Andy Burns

as electricity is almost 4 x the cost of gas for the same amount of
energy, your energy bills will be higher.....

You're not allowing anything for the CoP of the heatpump?

Even when you do, it turns out worse. Or so my friend who bought an up
to date eco-house told me.

Until we have nuclear electricity a heat pump inst worth it, and when we
have nuclear electricity we wont need a heat pump anyway.

[David]

Post by SH

Post by David
I know, I know, piece of string etc.
A distantly related family member has had a "green energy upgrade" free
of charge from the local council.
It consists of solar panels, a hybrid system of air source heat pump
and gas boiler.
She is now struggling to pay the energy bills.
Reportedly £350 a month, but further information being sought.
Also trying to find out what the bills were prior to the "free" upgrade.
We have a (modified) 1930s 3 bed semi with good insulation (especially
after the extension), good solar gain, gas heating and hob, electric
cooker and microwave.
Our annual predicted bill this month is just over £2,500.
Just over £300 for the coldest months of the year, but considerably
less in the summer.
I am thinking that solar panels and an air source heat pump should
reduce overall running costs.
However it is possible that a poor installation would actually increase
annual costs.
In which case the installation would not be appropriate.
I am now asking if anyone has an "average" 1930s 3 bed semi, and if so
what the energy bills look like over the year.
Just for a comparison, to see if the costs in her case are abnormally high.
If her bills have gone up significantly after a "free" installation
then that opens a whole can of worms.
Cheers
Dave R

switching from a gas fired heating & hot water system to an air source
heat pump actually worsens your EPC rating and as electricity is almost
4 x the cost of gas for the same amount of energy, your energy bills
will be higher.....

I am intrigued by the hybrid system of a gas boiler and an air source heat
pump.

There must (should?) be some fancy footwork to decide what to use.

In the absence of battery storage (which there isn't) I would assume that
the gas would be used any time the solar panels were not generating enough
to drive the ASHP.
However I sometimes take a simplistic view.

Cheers



Dave R

[Andy Burns]

Post by David
In the absence of battery storage (which there isn't) I would assume that
the gas would be used any time the solar panels were not generating enough
to drive the ASHP.

PV is unlikely to ever generate enough to run an ASHP, assuming a not
brilliantly insulated 30's semi, that could require a 10kW unit, so the
PV will just offset some of the electricity costs over the year, and
sell some unused power back to the grid.

[David]

Post by Andy Burns

Post by David
In the absence of battery storage (which there isn't) I would assume
that the gas would be used any time the solar panels were not
generating enough to drive the ASHP.

PV is unlikely to ever generate enough to run an ASHP, assuming a not
brilliantly insulated 30's semi, that could require a 10kW unit, so the
PV will just offset some of the electricity costs over the year, and
sell some unused power back to the grid.

So it seems sensible to use the ASHP when electricity is being generated
to partially offset the cost, and use the gas when there is no electricity
being generated.

Else why the hybrid system?

Unless the ASHP is run using off peak electricity and the gas is used to
top up.

Cheers



Dave R

[Andy Burns]

Post by David
So it seems sensible to use the ASHP when electricity is being generated
to partially offset the cost, and use the gas when there is no electricity
being generated.
Else why the hybrid system?
Unless the ASHP is run using off peak electricity and the gas is used to
top up.

All sorts is possible, you may have a lot of homework to do ...

[David]

Post by Andy Burns

Post by David
So it seems sensible to use the ASHP when electricity is being
generated to partially offset the cost, and use the gas when there is
no electricity being generated.
Else why the hybrid system?
Unless the ASHP is run using off peak electricity and the gas is used
to top up.

All sorts is possible, you may have a lot of homework to do ...

<https://www.worcester-bosch.co.uk/hybrid-systems#:~:text=A%20hybrid%
20heating%20and%20hot%20water%20system%20is,boiler%20and%20an%20air%20to%
20water%20heat%20pump.>

That is my first homework assignment.

Apparently you can install an ASHP without any major modifications if you
also have a combi to handle the difficult stuff.

No larger radiators, not hot water store.

Just use the ASHP as background heating and use the combi boiler for hot
water and topping up the central heating when the ASHP can't cope.

Smack of greenwashing to me.

Cheers



Dave R

[RJH]

Post by Andy Burns

Post by David
So it seems sensible to use the ASHP when electricity is being
generated to partially offset the cost, and use the gas when there is
no electricity being generated.
Else why the hybrid system?
Unless the ASHP is run using off peak electricity and the gas is used
to top up.

All sorts is possible, you may have a lot of homework to do ...

<https://www.worcester-bosch.co.uk/hybrid-systems#:~:text=A%20hybrid%>
20heating%20and%20hot%20water%20system%20is,boiler%20and%20an%20air%20to%
20water%20heat%20pump.>
That is my first homework assignment.

Ah right, I live and learn! Seems diametrically opposed to the 'eco' aspect of
ASHP schemes, though. And 2 lots of heating plant to maintain. Look odd from a
quick look.

[Theo]

Post by RJH

Post by Andy Burns
All sorts is possible, you may have a lot of homework to do ...

<https://www.worcester-bosch.co.uk/hybrid-systems#:~:text=A%20hybrid%>
20heating%20and%20hot%20water%20system%20is,boiler%20and%20an%20air%20to%
20water%20heat%20pump.>
That is my first homework assignment.

Ah right, I live and learn! Seems diametrically opposed to the 'eco' aspect of
ASHP schemes, though. And 2 lots of heating plant to maintain. Look odd from a
quick look.

Shocker: boiler company wants to sell boilers. They've done this kind of
distraction before with 'hydrogen ready' boilers - spoiler, hydrogen heating
isn't going to be a thing. But it gets the punters to install a 'future
proof' bog standard gas boiler.

I haven't heard of anyone with a Worcester-Bosch heatpump, they seem to be a
bit of an also-ran. They buy them in from someone else I think.

Theo

[alan_m]

Post by Theo
Shocker: boiler company wants to sell boilers. They've done this kind of
distraction before with 'hydrogen ready' boilers - spoiler, hydrogen heating
isn't going to be a thing. But it gets the punters to install a 'future
proof' bog standard gas boiler.

It's likely to be 90% natural gas and a 10% hydrogen (maybe 80/20%) mix
at best and not the misleading 100% hydrogen green hype.

[Andrew]

Post by alan_m

Shocker: boiler company wants to sell boilers.  They've done this kind of
distraction before with 'hydrogen ready' boilers - spoiler, hydrogen heating
isn't going to be a thing.  But it gets the punters to install a 'future
proof' bog standard gas boiler.

It's likely to be 90% natural gas and a 10% hydrogen (maybe 80/20%) mix
at best and not the misleading 100% hydrogen green hype.

By the time it gets to the end-user, it will be closer to 100% natural
gas, unless they replace all the nations underground pipework. There
are millions of houses that still have bits of 3/4 screwed iron and
those pesky H2 molecules are just going to whizz out of the joints.

[David Wade]

Post by Andrew

Post by alan_m

Shocker: boiler company wants to sell boilers.  They've done this kind of
distraction before with 'hydrogen ready' boilers - spoiler, hydrogen heating
isn't going to be a thing.  But it gets the punters to install a 'future
proof' bog standard gas boiler.

It's likely to be 90% natural gas and a 10% hydrogen (maybe 80/20%)
mix at best and not the misleading 100% hydrogen green hype.

By the time it gets to the end-user, it will be closer to 100% natural
gas, unless they replace all the nations underground pipework. There
are millions of houses that still have bits of 3/4 screwed iron and
those pesky H2 molecules are just going to whizz out of the joints.

Where I live the seem to be replacing all the underground pipe..

Dave

[Joe]

On Sat, 26 Apr 2025 17:57:56 +0100

Post by Andrew

Post by alan_m

Shocker: boiler company wants to sell boilers.  They've done this
kind of distraction before with 'hydrogen ready' boilers -
spoiler, hydrogen heating
isn't going to be a thing.  But it gets the punters to install a
'future proof' bog standard gas boiler.

It's likely to be 90% natural gas and a 10% hydrogen (maybe 80/20%)
mix at best and not the misleading 100% hydrogen green hype.

By the time it gets to the end-user, it will be closer to 100% natural
gas, unless they replace all the nations underground pipework. There
are millions of houses that still have bits of 3/4 screwed iron and
those pesky H2 molecules are just going to whizz out of the joints.

Don't forget that until the 70s, the gas piped into homes was derived
from coal and was about 50% hydrogen. Pipework was pretty much all iron.

[Alan Lee]

Post by Joe
Don't forget that until the 70s, the gas piped into homes was derived
from coal and was about 50% hydrogen. Pipework was pretty much all iron.

But at nowhere near the pressure required for modern hydrogen enriched gas.

[Vir Campestris]

Post by Theo
Shocker: boiler company wants to sell boilers. They've done this kind of
distraction before with 'hydrogen ready' boilers - spoiler, hydrogen heating
isn't going to be a thing. But it gets the punters to install a 'future
proof' bog standard gas boiler.
I haven't heard of anyone with a Worcester-Bosch heatpump, they seem to be a
bit of an also-ran. They buy them in from someone else I think.

Town gas had a fair bit of hydrogen in it. North sea conversion was just
re-jetting - why wouldn't it be the same for a methane-hydrogen blend?
Or even put hydrogen?

Andy

[Theo]

Post by Vir Campestris

Post by Theo
Shocker: boiler company wants to sell boilers. They've done this kind of
distraction before with 'hydrogen ready' boilers - spoiler, hydrogen heating
isn't going to be a thing. But it gets the punters to install a 'future
proof' bog standard gas boiler.
I haven't heard of anyone with a Worcester-Bosch heatpump, they seem to be a
bit of an also-ran. They buy them in from someone else I think.

Town gas had a fair bit of hydrogen in it. North sea conversion was just
re-jetting - why wouldn't it be the same for a methane-hydrogen blend?
Or even put hydrogen?

I think that's what they mean by 'hydrogen ready' - either switch the jets
over or the jets are designed to work with hydrogen. But they're really
using it as a smokescreen because home heating by hydrogen isn't happening.

The CMA gave them a slap:
https://www.gov.uk/government/news/investigation-into-boiler-company-over-green-claims
https://www.gov.uk/cma-cases/worcester-bosch-consumer-protection-case

Theo

[RJH]

Post by David

Post by SH

Post by David
I know, I know, piece of string etc.
A distantly related family member has had a "green energy upgrade" free
of charge from the local council.
It consists of solar panels, a hybrid system of air source heat pump
and gas boiler.
She is now struggling to pay the energy bills.
Reportedly £350 a month, but further information being sought.
Also trying to find out what the bills were prior to the "free" upgrade.

That'd be outrageous for anything other than a huge poorly insulated detached
house. The 'green upgade' wouldn't necessarily result in cost savings - as
mentioned elsewhere, the ASHP roughly matches the cost of gas overall. I'm
guessing the £350 is some sort of billing anomaly.

I'd guess the solar panels might give a £30-£50/month advantage over
pre-retrofit setup, and the ASHP no overall cost advantage.
The retention of gas, and a gas boiler, is odd. The way to cost savings is to
do away with gas, and save on the standing charge at the very least. So I'm
not sure what part of the design process that's all about.

Post by David

Post by SH

Post by David
We have a (modified) 1930s 3 bed semi with good insulation (especially
after the extension), good solar gain, gas heating and hob, electric
cooker and microwave.
Our annual predicted bill this month is just over £2,500.
Just over £300 for the coldest months of the year, but considerably
less in the summer.

Difficult to say. £2500 isn't outrageous, but is on the high side. Depends on
your personal needs/habits as much as anything.

Post by David

Post by SH

Post by David
I am thinking that solar panels and an air source heat pump should
reduce overall running costs.

Solar panels, certainly, especially with a battery. But, and from my
experience, going into solar on a hard cost/return basis makes the whole thing
marginal at best, unless you can DIY install.

ASHP? Well . . .

Post by David

Post by SH

Post by David
However it is possible that a poor installation would actually increase
annual costs.
In which case the installation would not be appropriate.

Indeed. It needs a very careful assessment of the current system and its
ability to heat satisfactorily at relatively low radiator temperatures. Then
you'd need to look at insulation and ventilation.

It's not exactly rocket science but does need to be considered as a whole
heat/insulate/ventilate system. A 30s semi isn't the worst to retrofit, but
will likely have challenges.

Post by David

Post by SH

Post by David
I am now asking if anyone has an "average" 1930s 3 bed semi, and if so
what the energy bills look like over the year.
Just for a comparison, to see if the costs in her case are abnormally high.
If her bills have gone up significantly after a "free" installation
then that opens a whole can of worms.
Cheers

Overall, they shouldn't. As mentioned above, I'd expect them to go down by
about £40/month because of the solar. The gas situation needs to be clarified.

If it turns out they have gone up significantly I'd look very closely at the
ASHP installation, and monitor the energy use of the 'pump.

Post by David

Post by SH

Post by David
Dave R

switching from a gas fired heating & hot water system to an air source
heat pump actually worsens your EPC rating and as electricity is almost
4 x the cost of gas for the same amount of energy, your energy bills
will be higher.....

I am intrigued by the hybrid system of a gas boiler and an air source heat
pump.

Yes, me too. I follow the whole retrofit/grants thing reasonably closely and
I've not seen a 'hybrid' example. If you happen to find out details of the
scheme/council I'd appreciate it if you could post . . .

Post by David
There must (should?) be some fancy footwork to decide what to use.
In the absence of battery storage (which there isn't) I would assume that
the gas would be used any time the solar panels were not generating enough
to drive the ASHP.

They could only ever meet a (probably) 13A load - ASHP can go way beyond that.
And the highest demand is obviously in the winter, when there's no sun.

Post by David
However I sometimes take a simplistic view.

Not at all - solar isn't really going to help *directly* drive an ASHP to a
significant extent. Most of the support will come from hot water heating when
the sun's out. And indirect support for costs through export to the grid.

[Alan Lee]

Post by David
I am intrigued by the hybrid system of a gas boiler and an air source heat
pump.
There must (should?) be some fancy footwork to decide what to use.

The basic config allows the ASHP to signal the boiler to turn on when
the outside temperature reaches a low set point, this varies by Make,
typically 5 degrees or so, just when the COP of the HP is going to take
a hit, so it is cheaper at that point to use the gas boiler.

A truly smart system can be fitted that will automatically allow
whatever energy source is the cheapest at that time to be used, for
example, the temperature may be 2 degrees outside, but a cheap rate of
electric is available, so the system uses the HP at that time as it is
the cheapest way of heating, even if the COP is only 2.5 at that outside
temperature. Solar can be integrated into the system too.

[alan_m]

Post by Alan Lee

Post by David
I am intrigued by the hybrid system of a gas boiler and an air source heat
pump.
There must (should?) be some fancy footwork to decide what to use.

The basic config allows the ASHP to signal the boiler to turn on when
the outside temperature reaches a low set point, this varies by Make,
typically 5 degrees or so, just when the COP of the HP is going to take
a hit, so it is cheaper at that point to use the gas boiler.
A truly smart system can be fitted that will automatically allow
whatever energy source is the cheapest at that time to be used, for
example, the temperature may be 2 degrees outside, but a cheap rate of
electric is available, so the system uses the HP at that time as it is
the cheapest way of heating, even if the COP is only 2.5 at that outside
temperature. Solar can be integrated into the system too.

But can you get a £7.5k grant (or other social grant) for such a system?

[Alan Lee]

Post by SH
switching from a gas fired heating & hot water system to an air source
heat pump actually worsens your EPC rating and as electricity is almost
4 x the cost of gas for the same amount of energy, your energy bills
will be higher.....

Firstly, no, they shoudlnt be higher. Read the original post. It is a
hybrid system, with an ASHP and a gas boiler. The gas boiler takes over
the HW/CH when the temperature falls below a certian outdoor
temperature, usually 5 or degrees C., the point where the efficiency of
the ASHP drops to belwo that of the gas boiler.
This system should be more efficient than a single gas boiler, or a
single ASHP, as the system uses the cheapest item to do the heating as
and when necessary. If it is integrated to the solar output, then it
should be a lot more efficient, and cheaper than a gas boiler alone.

Even with just an ASHP, the total energy bills should be less than with
a gas boiler, as the house now has solar panels, and even the worst ASHP
on the market can achieve a COP of 3.5, add in the solar, and the bills
should be a lot less than the combined electric and gas bills were
before the upgrade.

[Theo]

Post by David
I know, I know, piece of string etc.
A distantly related family member has had a "green energy upgrade" free of
charge from the local council.
It consists of solar panels, a hybrid system of air source heat pump and
gas boiler.
She is now struggling to pay the energy bills.
Reportedly £350 a month, but further information being sought.
Also trying to find out what the bills were prior to the "free" upgrade.

1960s semi chalet bungalow with loft conversion here, ~110m2 - that's a bit
bigger than the average Barratt idea of a 3 bed semi (~80m2) but in line
with some 1930s ones. Loft insulation is mediocre because of the conversion
(and loft access is a PITA to fix that), but have cavity wall insulation.
Uninsulated concrete floor.

13kW ASHP installed Dec 2021, so that's 1+12+12+12+4 = 41 months
Off the gas grid, so just electricity - replaced an oil boiler.

Consumption since 1 Dec 2021:

ASHP only: 11322.86kWh
Immersion heater (legionella cycle plus occasional free power from Octopus):
431.8kWh

Works out to be 11754.66kWh.

Let's say the price cap is 25p/kWh.

Total cost for heat over ~4 winters = £2938.67 at current rates.
Average monthly cost for heat and hot water = £71

If we take the winter to be 3 months and assume minimal heat the rest of the
year (ie ignoring hot water and spring/autumn heat), works out to be £244
for the winter months.


I would guess somebody is looking at the peak winter consumption and
panicking, without realising that you don't need very much heat the rest of
the year.

My recent billed consumption for each month end (bill date is mid-month, ie
'Sep 24' is ~15 Sep to 15 Oct) have been:

Apr 24: £117
May 24: £100
Jun 24: £89
Jul 24: £92
Aug 24: £91
Sep 24: £103
Oct 24: £138
Nov 24: £215
Dec 24: £269
Jan 25: £293
Feb 25: £221

(in Mar 24 and Mar 25 they did some complicated billing recalculation and I
can't see the cost at a glance. But guess it'll be somewhere between Feb
and Apr)

This includes all the other electrical stuff like computers, not just
heating.

Post by David
I am thinking that solar panels and an air source heat pump should reduce
overall running costs.
However it is possible that a poor installation would actually increase
annual costs.
In which case the installation would not be appropriate.

The hybrid gas thing is a worrying point for me. If you live in a farmhouse
or a mansion then keeping gas may make sense, but otherwise it's just
needless complexity. If they don't have space for a hot water cylinder and
kept their combi boiler then I suppose that might be a reason.

(you can find a lot of places for a hot water cylinder nowadays, including
in the eaves space in a loft conversion or in kitchen cupboards, so I think
even that's a mark of not trying hard enough)

Post by David
I am now asking if anyone has an "average" 1930s 3 bed semi, and if so
what the energy bills look like over the year.
Just for a comparison, to see if the costs in her case are abnormally high.

When was the system installed? Was it during the winter by any chance? In
which case not surprising it's going to take more when it's cold. Did they
happen to get a smart meter at the same time?

If you don't pay attention to your meters then it's easy to average out the
coldest part of the winter with the mild autumn and not realise that
consumption spikes on freezing days. A clear day when it's below zero can
take a lot more than the next day when it's cloudy and 5C. It just
depends on run of the winter how many of each you get - but it will be a
mix. Overall, the mild days tend to outweigh the freezing ones.

Theo

[SteveW]

Post by Theo

Post by David
I know, I know, piece of string etc.
A distantly related family member has had a "green energy upgrade" free of
charge from the local council.
It consists of solar panels, a hybrid system of air source heat pump and
gas boiler.
She is now struggling to pay the energy bills.
Reportedly £350 a month, but further information being sought.
Also trying to find out what the bills were prior to the "free" upgrade.

1960s semi chalet bungalow with loft conversion here, ~110m2 - that's a bit
bigger than the average Barratt idea of a 3 bed semi (~80m2) but in line
with some 1930s ones. Loft insulation is mediocre because of the conversion
(and loft access is a PITA to fix that), but have cavity wall insulation.
Uninsulated concrete floor.
13kW ASHP installed Dec 2021, so that's 1+12+12+12+4 = 41 months
Off the gas grid, so just electricity - replaced an oil boiler.
ASHP only: 11322.86kWh
431.8kWh
Works out to be 11754.66kWh.
Let's say the price cap is 25p/kWh.

That's fairly close to our annual gas consumption for heating and hot
water (1930's semi, 3 to 5 occupants depending who's home from
university, wife in 24 hours a day due to disability). So with the cost
differential between gas and electricity, it's pretty close in cost.

Just the extra capital cost of the ASHP and installation to skew the
figures.

[RJH]

Post by SteveW

Post by Theo
ASHP only: 11322.86kWh
431.8kWh
Works out to be 11754.66kWh.
Let's say the price cap is 25p/kWh.

That's fairly close to our annual gas consumption for heating and hot
water (1930's semi, 3 to 5 occupants depending who's home from
university, wife in 24 hours a day due to disability). So with the cost
differential between gas and electricity, it's pretty close in cost.

3 bed 1920s semi, reasonably insulated, combi gas/8 panel battery solar, May
2024 - April 2025:

Electricity: 1000kW/h
Gas: 5400kW/h

Direct debit about £70/month, less about £200/pa I'm expecting from solar
export.

This is fairly typical for me (sole occupant most of the time) despite some
very different use patterns over the years. This year I heated the whole house
throughout the winter to about 14C in the day, topping up individual rooms as
I used them with electric heaters, and heating the whole house to about 18C in
the evenings from the combi.

A vast variable here is the 14C/18C. Most people I know heat their homes to
something over 20C whenever they're at home. I actually find that
uncomfortably warm most of the time. It's just for a couple of hours in the
evening when I'm sat still reading etc. I like it warmer.

Other years I've tried zoning, no electric heating, switching all heating off
for various periods. For reasons I've yet to pin down, (adjusted) costs and
overall consumption has stayed pretty similar.

[Theo]

Post by SteveW

Post by Theo

Post by David
I know, I know, piece of string etc.
A distantly related family member has had a "green energy upgrade" free of
charge from the local council.
It consists of solar panels, a hybrid system of air source heat pump and
gas boiler.
She is now struggling to pay the energy bills.
Reportedly £350 a month, but further information being sought.
Also trying to find out what the bills were prior to the "free" upgrade.

1960s semi chalet bungalow with loft conversion here, ~110m2 - that's a bit
bigger than the average Barratt idea of a 3 bed semi (~80m2) but in line
with some 1930s ones. Loft insulation is mediocre because of the conversion
(and loft access is a PITA to fix that), but have cavity wall insulation.
Uninsulated concrete floor.
13kW ASHP installed Dec 2021, so that's 1+12+12+12+4 = 41 months
Off the gas grid, so just electricity - replaced an oil boiler.
ASHP only: 11322.86kWh
431.8kWh
Works out to be 11754.66kWh.
Let's say the price cap is 25p/kWh.

That's fairly close to our annual gas consumption for heating and hot
water (1930's semi, 3 to 5 occupants depending who's home from
university, wife in 24 hours a day due to disability). So with the cost
differential between gas and electricity, it's pretty close in cost.

ITYM close in money terms, not in kWh terms? Our pre-ASHP EPC (for what
it's worth) says heating would have needed 11200kWh pa, and 2700kWh pa for
hot water. We've achieved less than that over 4 winters, making the SCOP
roughly 4.7 (an overestimate, as there's from now until December to
make it a full 4 years, but heating demand until then is likely to be
limited apart from maybe November)

Post by SteveW
Just the extra capital cost of the ASHP and installation to skew the
figures.

Indeed. A big chunk of that is covered by the Boiler Upgrade Scheme grant
nowadays. Makes it roughly comparable with a gas boiler replacement, or
cheaper in some cases.

Theo

[RJH]

Post by Theo

Post by SteveW
Just the extra capital cost of the ASHP and installation to skew the
figures.

Indeed. A big chunk of that is covered by the Boiler Upgrade Scheme grant
nowadays. Makes it roughly comparable with a gas boiler replacement, or
cheaper in some cases.

Not in my experience. I got quotes around £15000 for the ASHP/HW cylinder,
making my contribution after the grant £7500.

A decent gas boiler replacement < £3000.

[alan_m]

Post by RJH

Post by Theo

Post by SteveW
Just the extra capital cost of the ASHP and installation to skew the
figures.

Indeed. A big chunk of that is covered by the Boiler Upgrade Scheme grant
nowadays. Makes it roughly comparable with a gas boiler replacement, or
cheaper in some cases.

Not in my experience. I got quotes around £15000 for the ASHP/HW cylinder,
making my contribution after the grant £7500.
A decent gas boiler replacement < £3000.

My gas boiler replacement cost just around £3000 and that included
moving it to a new location and removing and disposal of redundant pipework.

I read recently that the average cost of installing an ASHP from Octopus
was in the region of £11k (incl the £7.5k grant).

[RJH]

Post by alan_m

Post by RJH

Post by Theo

Post by SteveW
Just the extra capital cost of the ASHP and installation to skew the
figures.

Indeed. A big chunk of that is covered by the Boiler Upgrade Scheme grant
nowadays. Makes it roughly comparable with a gas boiler replacement, or
cheaper in some cases.

Not in my experience. I got quotes around £15000 for the ASHP/HW cylinder,
making my contribution after the grant £7500.
A decent gas boiler replacement <£3000.> My gas boiler replacement cost just
around £3000 and that included

moving it to a new location and removing and disposal of redundant pipework.
I read recently that the average cost of installing an ASHP from Octopus
was in the region of £11k (incl the £7.5k grant).

OK, if I'm reading that correctly, makes the decision to go ASHP much more
attractive - roughly equivalent to gas boiler replacement.

I enquired about a year ago, the shortage of installers meant prices were
inflated, and the grants were pretty much universal. The move will be towards
an element of means testing I feel. But for now, I think pretty much anyone
can get the grant.

[Andrew]

Post by Theo

Post by David
I know, I know, piece of string etc.
A distantly related family member has had a "green energy upgrade" free of
charge from the local council.
It consists of solar panels, a hybrid system of air source heat pump and
gas boiler.
She is now struggling to pay the energy bills.
Reportedly £350 a month, but further information being sought.
Also trying to find out what the bills were prior to the "free" upgrade.

1960s semi chalet bungalow with loft conversion here, ~110m2 - that's a bit
bigger than the average Barratt idea of a 3 bed semi (~80m2) but in line
with some 1930s ones. Loft insulation is mediocre because of the conversion
(and loft access is a PITA to fix that), but have cavity wall insulation.
Uninsulated concrete floor.
13kW ASHP installed Dec 2021, so that's 1+12+12+12+4 = 41 months
Off the gas grid, so just electricity - replaced an oil boiler.
ASHP only: 11322.86kWh
431.8kWh
Works out to be 11754.66kWh.

Blimey, I use about 3000 KwH per year and for a about 20 years
since I ripped out the Baxi Bermuda back boiler and most of
the pipework (don't ask!), that includes minimal heating, and
only one room properly warm in winter.

I have 300mm of insulation in the loft, the front (North) wall
has 80mm of celotext on the inside downstairs from slab up to
ceiling + PB. I dug out the screed of the solid ground floor in 2011
and laid another 1200 gauge DP plus 3x2 battens vertically set,
concrete screwed into the slab with 250mm gaps infilled with
70mm Quinntherm + 18mm hardwood floor.

Most of my heat loss is through the gable end (east), via the
brick+65mm rockwill-filled cavity+inner block, and old
aluminium DG patio doors and a couple of original Boulton and
Paul single glazed timber windows.

The party wall is a cavity wall and there is still some air-
leakage through that (it was awful back in 1992), but now both
semis have cavity wall insulation that has been massively
reduced.

At the moment I am using about 5 kwH /day, sometimes down to 3
if I am out and about and the weather is warm. Watching YouTube
or using the computer much of the day pushes it up a bit.

I have a 37 degree pitch due-south-facing roof so solar PV
and a battery system would 'work' for me, but I don't have an
EV so the cost/benefit equation is tricky.

The big problem with heat pumps is the need to have quite a lot
of space for the internal pressure vessels and pumps etc, over
and over the HWC. I have the latter, but where did you put all
the other gubbins in your bungalow ?

Andrew

[Theo]

Post by Andrew

Post by Theo
ASHP only: 11322.86kWh
431.8kWh
Works out to be 11754.66kWh.

Blimey, I use about 3000 KwH per year and for a about 20 years
since I ripped out the Baxi Bermuda back boiler and most of
the pipework (don't ask!), that includes minimal heating, and
only one room properly warm in winter.

That's over 4 winters, so about 3000kWh per year heating and hot water.
Heats the whole house 24/7/365, ie it's climate control - usually set to
about 19C. It comes on when needed to boost the temp to 19C, no timers
nothing. It's always comfortable, never cold.

Post by Andrew
I have a 37 degree pitch due-south-facing roof so solar PV
and a battery system would 'work' for me, but I don't have an
EV so the cost/benefit equation is tricky.

Yes, it's marginal. I'm looking at doing a bargain basement DIY solar
install for the garage - 'second' panels about £35, I need to find a ~£50
used inverter and it'll be worth it just to cover standby power.

Post by Andrew
The big problem with heat pumps is the need to have quite a lot
of space for the internal pressure vessels and pumps etc, over
and over the HWC. I have the latter, but where did you put all
the other gubbins in your bungalow ?

There was a cylinder in the airing cupboard. This was replaced by combined
200l cylinder and 50l buffer, pumps and valves in front, expansion vessels
on the wall above. It lost about a foot of shelf space as the cylinder got
taller, but the space above is still useful for storage, eg duvets.

Theo

[Andrew]

Post by Theo

Post by Andrew

Post by Theo
ASHP only: 11322.86kWh
431.8kWh
Works out to be 11754.66kWh.

Blimey, I use about 3000 KwH per year and for a about 20 years
since I ripped out the Baxi Bermuda back boiler and most of
the pipework (don't ask!), that includes minimal heating, and
only one room properly warm in winter.

That's over 4 winters, so about 3000kWh per year heating and hot water.
Heats the whole house 24/7/365, ie it's climate control - usually set to
about 19C. It comes on when needed to boost the temp to 19C, no timers
nothing. It's always comfortable, never cold.

Post by Andrew
I have a 37 degree pitch due-south-facing roof so solar PV
and a battery system would 'work' for me, but I don't have an
EV so the cost/benefit equation is tricky.

Yes, it's marginal. I'm looking at doing a bargain basement DIY solar
install for the garage - 'second' panels about £35, I need to find a ~£50
used inverter and it'll be worth it just to cover standby power.

Post by Andrew
The big problem with heat pumps is the need to have quite a lot
of space for the internal pressure vessels and pumps etc, over
and over the HWC. I have the latter, but where did you put all
the other gubbins in your bungalow ?

There was a cylinder in the airing cupboard. This was replaced by combined
200l cylinder and 50l buffer, pumps and valves in front, expansion vessels
on the wall above. It lost about a foot of shelf space as the cylinder got
taller, but the space above is still useful for storage, eg duvets.
Theo

So you lost your airing cupboard, whereas I have an airing cupboard
but nowhere else to take its place.

If I replaced my standard HWC with a 200 litre one, the simpson
joist hangers that strap the lateral 9x2.5 inch joists to the one
running along the top of the wall that is part of the stairs would
probably fail !.

Idiot builders in 1976 used 4 inch round wire nails to 'fix' the
hangers, with a gap of up to 0.5 inch between the butt end of the
lateral flooring joists and the supporting joist sitting on an
internal partition wall (also strapped at each end to another
lateral pair of doubled joists). No 45 degree cross nailing with
any sort of nail into the butt ends either. Real botch job.

You can seen from the distortion of the joist hangers that they
are were close to failure back in 1976 (upstairs partition walls
are 3 inch cinder blocks built right onto the chipboard flooring)

[Theo]

Post by Andrew

Post by Theo
There was a cylinder in the airing cupboard. This was replaced by combined
200l cylinder and 50l buffer, pumps and valves in front, expansion vessels
on the wall above. It lost about a foot of shelf space as the cylinder got
taller, but the space above is still useful for storage, eg duvets.

So you lost your airing cupboard, whereas I have an airing cupboard
but nowhere else to take its place.

Didn't lose it as it's double-width. The cylinder already occupied one
half, so only lost about 10% more of the total. If the install didn't have
a buffer tank (it didn't need one, but the ASHP manufacturer was a bit lazy)
then it would have been the same as what we had before, just with a thicker
jacket on the cylinder.

Could you put a hot water tank in your loft? There are horizontal unvented
cylinders, eg:
https://www.plumbnation.co.uk/horizontal-unvented-cylinders-295-0000

If you put it on top of a load bearing wall you shouldn't need to rely on
dodgy joists. Used to live somewhere that had a solar thermal system and a
300 litre upright cylinder in the loft, positioned over a solid wall.

Theo

[Andrew]

Post by Theo

Post by Andrew

Post by Theo
There was a cylinder in the airing cupboard. This was replaced by combined
200l cylinder and 50l buffer, pumps and valves in front, expansion vessels
on the wall above. It lost about a foot of shelf space as the cylinder got
taller, but the space above is still useful for storage, eg duvets.

So you lost your airing cupboard, whereas I have an airing cupboard
but nowhere else to take its place.

Didn't lose it as it's double-width. The cylinder already occupied one
half, so only lost about 10% more of the total. If the install didn't have
a buffer tank (it didn't need one, but the ASHP manufacturer was a bit lazy)
then it would have been the same as what we had before, just with a thicker
jacket on the cylinder.
Could you put a hot water tank in your loft? There are horizontal unvented
https://www.plumbnation.co.uk/horizontal-unvented-cylinders-295-0000
If you put it on top of a load bearing wall you shouldn't need to rely on
dodgy joists. Used to live somewhere that had a solar thermal system and a
300 litre upright cylinder in the loft, positioned over a solid wall.
Theo

No, it's a 1976 semi, about 80m2. The airing cupboard has a standard
36inch high HWC and a 600mm door. not much space behind and each side
of the tank, a bit more in front towards the door.

As previously mentioned, the lateral 1st floor flooring joists have
deflected about an inch where the tank is and the ends of the same
joists are badly connected to their front/back joist, so I cannot
consider a bigger HWC at that location.

Loft is 37 degree pitch and I have added 300mm of insulation plus
'decking' for storage so the headroom is even less. No supporting
internal walls. The eight metre span trusses sit on the front and
back walls.

Other than building a side extension, I think my only option is
an air->air heat pump and modern storage heaters, plus masses of
insulation, then think about solar PV and a battery.

[alan_m]

Post by David
I know, I know, piece of string etc.
A distantly related family member has had a "green energy upgrade" free of
charge from the local council.
It consists of solar panels, a hybrid system of air source heat pump and
gas boiler.
She is now struggling to pay the energy bills.
Reportedly £350 a month, but further information being sought.
Also trying to find out what the bills were prior to the "free" upgrade.
We have a (modified) 1930s 3 bed semi with good insulation (especially
after the extension), good solar gain, gas heating and hob, electric
cooker and microwave.
Our annual predicted bill this month is just over £2,500.
Just over £300 for the coldest months of the year, but considerably less
in the summer.
I am thinking that solar panels and an air source heat pump should reduce
overall running costs.
However it is possible that a poor installation would actually increase
annual costs.
In which case the installation would not be appropriate.
I am now asking if anyone has an "average" 1930s 3 bed semi, and if so
what the energy bills look like over the year.
Just for a comparison, to see if the costs in her case are abnormally high.
If her bills have gone up significantly after a "free" installation then
that opens a whole can of worms.

Is that £350 just for the coldest winter months or for all months?

I don't that there any grants for a hybrid ASHP+Gas for central heating.
Why would a properly designed ASHP need additional gas heating in a 3
bed semi?

[David]

Post by alan_m

Post by David
I know, I know, piece of string etc.
A distantly related family member has had a "green energy upgrade" free
of charge from the local council.
It consists of solar panels, a hybrid system of air source heat pump
and gas boiler.
She is now struggling to pay the energy bills.
Reportedly £350 a month, but further information being sought.
Also trying to find out what the bills were prior to the "free" upgrade.
We have a (modified) 1930s 3 bed semi with good insulation (especially
after the extension), good solar gain, gas heating and hob, electric
cooker and microwave.
Our annual predicted bill this month is just over £2,500.
Just over £300 for the coldest months of the year, but considerably
less in the summer.
I am thinking that solar panels and an air source heat pump should
reduce overall running costs.
However it is possible that a poor installation would actually increase
annual costs.
In which case the installation would not be appropriate.
I am now asking if anyone has an "average" 1930s 3 bed semi, and if so
what the energy bills look like over the year.
Just for a comparison, to see if the costs in her case are abnormally high.
If her bills have gone up significantly after a "free" installation
then that opens a whole can of worms.

Is that £350 just for the coldest winter months or for all months?
I don't that there any grants for a hybrid ASHP+Gas for central heating.
Why would a properly designed ASHP need additional gas heating in a 3
bed semi?

As posted up thread, the hybrid system seems to be aimed at minimal
installation cost.
No new plumbing and larger radiators.
No hot water storage.
So basically keep your existing system but add an additional heat source
to the mix (and tick a green credentials box).
The ASHP is (as far as I can see) equivalent to base load with gas used to
top up any heating demand above the capabilities of the ASHP and to
provide hot water.

I am not convinced of any major benefits beyond improving your carbon
footprint.

Cheers


Dave R

[Theo]

Post by David
As posted up thread, the hybrid system seems to be aimed at minimal
installation cost.
No new plumbing and larger radiators.
No hot water storage.
So basically keep your existing system but add an additional heat source
to the mix (and tick a green credentials box).
The ASHP is (as far as I can see) equivalent to base load with gas used to
top up any heating demand above the capabilities of the ASHP and to
provide hot water.

I suspect that isn't going to work very well. The ASHP wants to run at low
flow temps, ideally ~35C. A traditional boiler system is designed to run at
60-70C flow temps. If your radiators are right-sized for the boiler, they'll
be too small to extract much heat from the heat pump.

If you upgrade the radiators for the heat pump then the boiler can run at a
much lower flow temp (=more efficient), but you need a condensing boiler for
that. If the boiler is old enough that people are thinking of upgrading,
then possibly it's too old to condense (very much) or do weather
compensation. Also, as a combi, you need a very wide range of modulation -
because the combi will be sized for 30kW of hot water and not 1.5kW of heating
load.

If you don't do it right I think it's going to work out worse than one or
the other. You can't just slap in an ASHP on an existing combi system and
hope it to be efficient. Maybe there is a place for a combined system, but
both parts need to be designed to work together.

Now, if you installed air to air units (ie air conditioners that can do
heating) and kept the combi for the hot water only, then I could see some
advantages.

But if you are going to have an air2water system it's disadvantageous not to
have it do hot water too. I would be looking very hard for somewhere you
can put hot water storage - especially if you live in a house, where there's
more space than a flat.

Theo

[David]

Post by Theo

Post by David
As posted up thread, the hybrid system seems to be aimed at minimal
installation cost.
No new plumbing and larger radiators.
No hot water storage.
So basically keep your existing system but add an additional heat
source to the mix (and tick a green credentials box).
The ASHP is (as far as I can see) equivalent to base load with gas used
to top up any heating demand above the capabilities of the ASHP and to
provide hot water.

I suspect that isn't going to work very well. The ASHP wants to run at
low flow temps, ideally ~35C. A traditional boiler system is designed
to run at 60-70C flow temps. If your radiators are right-sized for the
boiler, they'll be too small to extract much heat from the heat pump.
<snip>
Theo

Which brings us back to the start of the thread, more or less.

It appears that a Council is supplying a hybrid system free of charge to
improve the carbon footprint of houses.
However this "worthy" activity doesn't seem to be reducing the energy
costs to the householder and may even be increasing them.

A link to Worcester Bosch upstream somewhere talks about adding ASHP
without modification to existing systems. i.e. No larger radiators, no hot
water storage. A Hybrid system.

I am charitably assuming that the ASHP will bring the radiators up to
around 30-40C and then the gas boiler will top this off to the design
temperature of the radiators if the house is cool/cold.
In theory this should reduce gas usage by substituting efficient use of
electricity in the CH.

As I have said, this looks like a fudge to me, to get an ASHP installed
without the expensive infrastructure modification required for a proper
full ASHP install. Otherwise known as greenwashing.

Further information awaited.

Thanks to all who have contributed.

Cheers


Dave R

[Theo]

Post by David
Which brings us back to the start of the thread, more or less.
It appears that a Council is supplying a hybrid system free of charge to
improve the carbon footprint of houses.
However this "worthy" activity doesn't seem to be reducing the energy
costs to the householder and may even be increasing them.
A link to Worcester Bosch upstream somewhere talks about adding ASHP
without modification to existing systems. i.e. No larger radiators, no hot
water storage. A Hybrid system.
I am charitably assuming that the ASHP will bring the radiators up to
around 30-40C and then the gas boiler will top this off to the design
temperature of the radiators if the house is cool/cold.
In theory this should reduce gas usage by substituting efficient use of
electricity in the CH.
As I have said, this looks like a fudge to me, to get an ASHP installed
without the expensive infrastructure modification required for a proper
full ASHP install. Otherwise known as greenwashing.

I suppose what they might be doing is installing a 'high temperature heat
pump'. Basically this is a two-stage unit, the first stage is like a
regular ASHP. The second stage takes the output at let's say 35C and then
does another compression cycle to raise the output water temps to 60+C,
possibly with a different refrigerant than in the first stage. That means
you can use your existing radiators etc with the 60C water, but you pay the
energy cost in terms of running what's effectively a second ASHP on top of
the first.

It may be that the cost of building two ASHPs in one box is now low enough
compared with replacing all the radiators, but you're always going to pay
for it in lost efficiency: the higher you have to run uphill to do the job,
the more energy it takes.

There are also some single-stage high temperature heat pumps, using R290
(propane) or R744 (CO2).

Not sure if this is single or two stage (it's R290):
https://cdn.shopify.com/s/files/1/2612/5402/files/CE-IVT9-EVI_Data_Sheet_QR.pdf?v=1717419237
(costs about £4k)

For a nominal 9kW HP (7C air in/35C water out), at -3C air you get 7kW at 35C
output, down to 5.4kW at 75C output. At 7C in/35C out the COP is 4.52 and
at 7C/75C it's down to 3.05.

So by skipping the one-time radiator upgrade cost you're paying 50% more on
your energy bill every year.

Post by David
Further information awaited.

Indeed, would be interesting to know the model of the ASHP.

Theo

[The Natural Philosopher]

Post by David
As I have said, this looks like a fudge to me, to get an ASHP installed
without the expensive infrastructure modification required for a proper
full ASHP install. Otherwise known as greenwashing.

Portugal, Spain and parts of France are without electricity right now.

Nothing to do with renewables. Oh no. Of course not.

[tony sayer]

Post by The Natural Philosopher

Post by David
As I have said, this looks like a fudge to me, to get an ASHP installed
without the expensive infrastructure modification required for a proper
full ASHP install. Otherwise known as greenwashing.

Portugal, Spain and parts of France are without electricity right now.
Nothing to do with renewables. Oh no. Of course not.

Not the Ruskis taking a practice before they sod up the UK grid;?..

[Joe]

On Mon, 28 Apr 2025 19:12:54 +0100

Post by tony sayer

Post by The Natural Philosopher

Post by David
As I have said, this looks like a fudge to me, to get an ASHP
installed without the expensive infrastructure modification
required for a proper full ASHP install. Otherwise known as
greenwashing.

Portugal, Spain and parts of France are without electricity right now.
Nothing to do with renewables. Oh no. Of course not.

Not the Ruskis taking a practice before they sod up the UK grid;?..

Why do you think Miliband needs help?

[The Natural Philosopher]

Post by Joe
On Mon, 28 Apr 2025 19:12:54 +0100

Post by tony sayer

Post by The Natural Philosopher

Post by David
As I have said, this looks like a fudge to me, to get an ASHP
installed without the expensive infrastructure modification
required for a proper full ASHP install. Otherwise known as
greenwashing.

Portugal, Spain and parts of France are without electricity right now.
Nothing to do with renewables. Oh no. Of course not.

Not the Ruskis taking a practice before they sod up the UK grid;?..

Why do you think Miliband needs help?

Precisely...anyway like Trump he is just another Russian asset anyway

[The Natural Philosopher]

Post by tony sayer

Post by The Natural Philosopher

Post by David
As I have said, this looks like a fudge to me, to get an ASHP installed
without the expensive infrastructure modification required for a proper
full ASHP install. Otherwise known as greenwashing.

Portugal, Spain and parts of France are without electricity right now.
Nothing to do with renewables. Oh no. Of course not.

Not the Ruskis taking a practice before they sod up the UK grid;?..

They and the EUs 'renewable energy obligation' have already *done* that...

[Andrew]

Post by David

Post by alan_m

Post by David
I know, I know, piece of string etc.
A distantly related family member has had a "green energy upgrade" free
of charge from the local council.
It consists of solar panels, a hybrid system of air source heat pump
and gas boiler.
She is now struggling to pay the energy bills.
Reportedly £350 a month, but further information being sought.
Also trying to find out what the bills were prior to the "free" upgrade.
We have a (modified) 1930s 3 bed semi with good insulation (especially
after the extension), good solar gain, gas heating and hob, electric
cooker and microwave.
Our annual predicted bill this month is just over £2,500.
Just over £300 for the coldest months of the year, but considerably
less in the summer.
I am thinking that solar panels and an air source heat pump should
reduce overall running costs.
However it is possible that a poor installation would actually increase
annual costs.
In which case the installation would not be appropriate.
I am now asking if anyone has an "average" 1930s 3 bed semi, and if so
what the energy bills look like over the year.
Just for a comparison, to see if the costs in her case are abnormally high.
If her bills have gone up significantly after a "free" installation
then that opens a whole can of worms.

Is that £350 just for the coldest winter months or for all months?
I don't that there any grants for a hybrid ASHP+Gas for central heating.
Why would a properly designed ASHP need additional gas heating in a 3
bed semi?

As posted up thread, the hybrid system seems to be aimed at minimal
installation cost.
No new plumbing and larger radiators.
No hot water storage.
So basically keep your existing system but add an additional heat source
to the mix (and tick a green credentials box).
The ASHP is (as far as I can see) equivalent to base load with gas used to
top up any heating demand above the capabilities of the ASHP and to
provide hot water.
I am not convinced of any major benefits beyond improving your carbon
footprint.
Cheers
Dave R

Might be easier to have an air-to-air heat pump, and avoid
any plumbing changes. Add solar PV and a battery and you have
cheap/free air con in summer and in winter use the overnight
tariffs to charge the battery or run the heat pump.

[David Wade]

Post by Andrew

Post by David

Post by alan_m

Post by David
I know, I know, piece of string etc.
A distantly related family member has had a "green energy upgrade" free
of charge from the local council.
It consists of solar panels, a hybrid system of air source heat pump
and gas boiler.
She is now struggling to pay the energy bills.
Reportedly £350 a month, but further information being sought.
Also trying to find out what the bills were prior to the "free" upgrade.
We have a (modified) 1930s 3 bed semi with good insulation (especially
after the extension), good solar gain, gas heating and hob, electric
cooker and microwave.
Our annual predicted bill this month is just over £2,500.
Just over £300 for the coldest months of the year, but considerably
less in the summer.
I am thinking that solar panels and an air source heat pump should
reduce overall running costs.
However it is possible that a poor installation would actually increase
annual costs.
In which case the installation would not be appropriate.
I am now asking if anyone has an "average" 1930s 3 bed semi, and if so
what the energy bills look like over the year.
Just for a comparison, to see if the costs in her case are abnormally high.
If her bills have gone up significantly after a "free" installation
then that opens a whole can of worms.

Is that £350 just for the coldest winter months or for all months?
I don't that there any grants for a hybrid ASHP+Gas for central heating.
   Why would a properly designed ASHP need additional gas heating in a 3
bed semi?

As posted up thread, the hybrid system seems to be aimed at minimal
installation cost.
No new plumbing and larger radiators.
No hot water storage.
So basically keep your existing system but add an additional heat source
to the mix (and tick a green credentials box).
The ASHP is (as far as I can see) equivalent to base load with gas used to
top up any heating demand above the capabilities of the ASHP and to
provide hot water.
I am not convinced of any major benefits beyond improving your carbon
footprint.
Cheers
Dave R

Might be easier to have an air-to-air heat pump, and avoid
any plumbing changes. Add solar PV and a battery and you have
cheap/free air con in summer and in winter use the overnight
tariffs to charge the battery or run the heat pump.

I think for many air-2-air heat pumps aka aircon would be the way to go.
I understand that as they don't need a high temperature difference they
retain their efficiency at lower outside temperatures. The main issue is
they don't heat the water.

Given many reports suggest that even with modifications like external
shutters, we are going to need aircon, the cost, even without a grant
was less than an air2water heat pump

Of course the government does not want us to have them, as they can be
used to cool, and they don't solve the hot water problem

Dave

[alan_m]

Post by Andrew
Might be easier to have an air-to-air heat pump, and avoid
any plumbing changes. Add solar PV and a battery and you have
cheap/free air con in summer and in winter use the overnight
tariffs to charge the battery or run the heat pump.

You cannot get a grant for air to air and for air con in summer.

[David Wade]

Post by alan_m

Post by Andrew
Might be easier to have an air-to-air heat pump, and avoid
any plumbing changes. Add solar PV and a battery and you have
cheap/free air con in summer and in winter use the overnight
tariffs to charge the battery or run the heat pump.

You cannot get a grant for air to air and for air con in summer.

you don't need it. cost is so much lower. grant is a total white wash. I
am sure they put the price up because they know you get a grant...

Dave

[Andrew]

Post by David Wade

Post by alan_m

Post by Andrew
Might be easier to have an air-to-air heat pump, and avoid
any plumbing changes. Add solar PV and a battery and you have
cheap/free air con in summer and in winter use the overnight
tariffs to charge the battery or run the heat pump.

You cannot get a grant for air to air and for air con in summer.

you don't need it. cost is so much lower. grant is a total white wash. I
am sure they put the price up because they know you get a grant...
Dave

That's what I suspect. And it may be that there is simply a jumper
inside somewhere that disables air-con.

[David]

Post by Andrew

Post by David Wade

Post by alan_m

Might be easier to have an air-to-air heat pump, and avoid any
plumbing changes. Add solar PV and a battery and you have cheap/free
air con in summer and in winter use the overnight tariffs to charge
the battery or run the heat pump.

You cannot get a grant for air to air and for air con in summer.

you don't need it. cost is so much lower. grant is a total white wash.
I am sure they put the price up because they know you get a grant...
Dave

That's what I suspect. And it may be that there is simply a jumper
inside somewhere that disables air-con.

I understand that you need planning permission for air to air.

Not for air to water.

Because the government doesn't want easy access to cooling in the summer.

Cheers



Dave R

[Tim+]

Post by David

Post by Andrew

Post by David Wade

Post by alan_m

Might be easier to have an air-to-air heat pump, and avoid any
plumbing changes. Add solar PV and a battery and you have cheap/free
air con in summer and in winter use the overnight tariffs to charge
the battery or run the heat pump.

You cannot get a grant for air to air and for air con in summer.

you don't need it. cost is so much lower. grant is a total white wash.
I am sure they put the price up because they know you get a grant...
Dave

That's what I suspect. And it may be that there is simply a jumper
inside somewhere that disables air-con.

I understand that you need planning permission for air to air.

No planning permission needs for a single air/air unit, but no grants if it
can provide cooling (as I understand it).

Tim

[Theo]

Post by Tim+

Post by David

Post by Andrew

Post by David Wade

Post by alan_m

Might be easier to have an air-to-air heat pump, and avoid any
plumbing changes. Add solar PV and a battery and you have cheap/free
air con in summer and in winter use the overnight tariffs to charge
the battery or run the heat pump.

You cannot get a grant for air to air and for air con in summer.

you don't need it. cost is so much lower. grant is a total white wash.
I am sure they put the price up because they know you get a grant...
Dave

That's what I suspect. And it may be that there is simply a jumper
inside somewhere that disables air-con.

I understand that you need planning permission for air to air.

No planning permission needs for a single air/air unit, but no grants if it
can provide cooling (as I understand it).

The issue last time I looked was that the grant requires a heat pump on the
MCS certified list, and no air to air units were.

I'm not sure whether air2air is covered anyway by the BUS grant anyway, as:
https://www.legislation.gov.uk/ukdsi/2022/9780348232349/regulation/9

"(2) A heat pump meets the suitability criteria in relation to the eligible
property, or a property to which regulation 14(1)(b) applies, for which it
is installed where—

(a)it provides heating—

(i)solely to that property, or to both that property and any related property, and

(ii)for the purpose of both space heating and hot water heating, using
liquid as a medium for delivering that heat,"


An air2air is pumping around a refrigerant, but at the point it's delivering
heat it's in the gas phase - once the heat is delivered it'll condense.
It's only when delivering cooling is the refrigerant in the liquid phase.

Theo

[David]

Post by Theo

Post by Tim+

Post by David

Post by Andrew

Post by David Wade

Post by alan_m

Might be easier to have an air-to-air heat pump, and avoid any
plumbing changes. Add solar PV and a battery and you have
cheap/free air con in summer and in winter use the overnight
tariffs to charge the battery or run the heat pump.

You cannot get a grant for air to air and for air con in summer.

you don't need it. cost is so much lower. grant is a total white wash.
I am sure they put the price up because they know you get a grant...
Dave

That's what I suspect. And it may be that there is simply a jumper
inside somewhere that disables air-con.

I understand that you need planning permission for air to air.

No planning permission needs for a single air/air unit, but no grants
if it can provide cooling (as I understand it).

The issue last time I looked was that the grant requires a heat pump on
the MCS certified list, and no air to air units were.
I'm not sure whether air2air is covered anyway by the BUS grant anyway,
as: https://www.legislation.gov.uk/ukdsi/2022/9780348232349/regulation/9
"(2) A heat pump meets the suitability criteria in relation to the
eligible property, or a property to which regulation 14(1)(b) applies,
for which it is installed where—
(a)it provides heating—
(i)solely to that property, or to both that property and any related property, and
(ii)for the purpose of both space heating and hot water heating, using
liquid as a medium for delivering that heat,"
An air2air is pumping around a refrigerant, but at the point it's
delivering heat it's in the gas phase - once the heat is delivered it'll
condense.
It's only when delivering cooling is the refrigerant in the liquid phase.
Theo

This was discussed some time ago, and my understanding is that you do need
to apply for permission to install an ASHP.
However the requirement was waived for heating only.

If I have enough energy I will search back for it.

Cheers



DAve R

[Andy Burns]

Post by David
my understanding is that you do need
to apply for permission to install an ASHP.
However the requirement was waived for heating only.
If I have enough energy I will search back for it.

I remember RevK (of A&A fame) fell foul of it

<https://www.revk.uk/2018/07/air-conditioning-at-home-planning.html>

[Theo]

Post by David
This was discussed some time ago, and my understanding is that you do need
to apply for permission to install an ASHP.
However the requirement was waived for heating only.

Yes. That's separate from being eligible for the grant. ie you can install
air2air for heating only without needing PP (as long as there's only one
outdoor unit), but you won't get a grant for it.

Theo

[RJH]

Post by Theo

Post by David
This was discussed some time ago, and my understanding is that you do need
to apply for permission to install an ASHP.
However the requirement was waived for heating only.

Yes. That's separate from being eligible for the grant. ie you can install
air2air for heating only without needing PP (as long as there's only one
outdoor unit), but you won't get a grant for it.

https://www.revk.uk/2018/07/air-conditioning-at-home-planning.html

. . . Andy Burns gave suggests that a cooling heat pump does:

'There is, however, a catch, and it is one even the council seem to be unaware
of most of the time, and that is G3(a) states "the air source heat pump is
used solely for heating purposes". That's right, an air-conditioning unit that
cools, or heats and cools, is not allowed under this permitted development, so
even if you have only one, it needs planning permission!'

[Theo]

Post by Andy Burns

Post by Theo

Post by David
This was discussed some time ago, and my understanding is that you do need
to apply for permission to install an ASHP.
However the requirement was waived for heating only.

Yes. That's separate from being eligible for the grant. ie you can install
air2air for heating only without needing PP (as long as there's only one
outdoor unit), but you won't get a grant for it.

https://www.revk.uk/2018/07/air-conditioning-at-home-planning.html

Yes, that's why I said 'air2air for heating only'. But I don't know if such
a thing exists, or how far you need to go to disable cooling.

(on mine there is no way to fully disable cooling, but it was configured to
be controlled by a dry contact. They then deleted all mention of cooling
from the manual including this input - hey presto it doesn't do cooling)

Theo

[The Natural Philosopher]

Post by David
I know, I know, piece of string etc.
A distantly related family member has had a "green energy upgrade" free of
charge from the local council.
It consists of solar panels, a hybrid system of air source heat pump and
gas boiler.
She is now struggling to pay the energy bills.
Reportedly £350 a month, but further information being sought.
Also trying to find out what the bills were prior to the "free" upgrade.
We have a (modified) 1930s 3 bed semi with good insulation (especially
after the extension), good solar gain, gas heating and hob, electric
cooker and microwave.
Our annual predicted bill this month is just over £2,500.
Just over £300 for the coldest months of the year, but considerably less
in the summer.
I am thinking that solar panels and an air source heat pump should reduce
overall running costs.
However it is possible that a poor installation would actually increase
annual costs.
In which case the installation would not be appropriate.
I am now asking if anyone has an "average" 1930s 3 bed semi, and if so
what the energy bills look like over the year.
Just for a comparison, to see if the costs in her case are abnormally high.
If her bills have gone up significantly after a "free" installation then
that opens a whole can of worms.
Cheers
Dave R

With electricity several times more expensive than gas and solar panels
being pointless in winter, heat pumps are way more expensive than gas
even in a building that is insulated to the nines.


]

[Andrew]

Post by The Natural Philosopher

Post by David
I know, I know, piece of string etc.
A distantly related family member has had a "green energy upgrade" free of
charge from the local council.
It consists of solar panels, a hybrid system of air source heat pump and
gas boiler.
She is now struggling to pay the energy bills.
Reportedly £350 a month, but further information being sought.
Also trying to find out what the bills were prior to the "free" upgrade.
We have a (modified) 1930s 3 bed semi with good insulation (especially
after the extension), good solar gain, gas heating and hob, electric
cooker and microwave.
Our annual predicted bill this month is just over £2,500.
Just over £300 for the coldest months of the year, but considerably less
in the summer.
I am thinking that solar panels and an air source heat pump should reduce
overall running costs.
However it is possible that a poor installation would actually increase
annual costs.
In which case the installation would not be appropriate.
I am now asking if anyone has an "average" 1930s 3 bed semi, and if so
what the energy bills look like over the year.
Just for a comparison, to see if the costs in her case are abnormally high.
If her bills have gone up significantly after a "free" installation then
that opens a whole can of worms.
Cheers
Dave R

With electricity several times more expensive than gas and solar panels
being pointless in winter, heat pumps are way more expensive than gas
even in a building that is insulated to the nines.
]

Well a full passive house, there should be so much insulation
that even storage rads might be all you need.

[JNugent]

Post by David
I know, I know, piece of string etc.
A distantly related family member has had a "green energy upgrade" free of
charge from the local council.
It consists of solar panels, a hybrid system of air source heat pump and
gas boiler.
She is now struggling to pay the energy bills.
Reportedly £350 a month, but further information being sought.
Also trying to find out what the bills were prior to the "free" upgrade.
We have a (modified) 1930s 3 bed semi with good insulation (especially
after the extension), good solar gain, gas heating and hob, electric
cooker and microwave.
Our annual predicted bill this month is just over £2,500.
Just over £300 for the coldest months of the year, but considerably less
in the summer.

Is that £300 per quarter or per month?

I suppose it must be per month, but the phrase "the coldest months"
could suggest otherwise.

I've just paid our Jan-Apr bills, About £330 for electricity and £420
for gas. If your bills are assessed monthly, our ££750 for the whole
quarter doesn't sound so bad, especially with all the electrical items
which are on more or less all the time here.

Post by David
I am thinking that solar panels and an air source heat pump should reduce
overall running costs.
However it is possible that a poor installation would actually increase
annual costs.
In which case the installation would not be appropriate.
I am now asking if anyone has an "average" 1930s 3 bed semi, and if so
what the energy bills look like over the year.
Just for a comparison, to see if the costs in her case are abnormally high.

We have just such a house, built about 1960, but definitely to the late
1920s - 1940 type pattern (the original owner had the pair built and
seemed to have preferred the older style).

I can easily sum the bills for the last four quarters (if that's a
helpful figure): £2880 (but we probably use more electricity than
average, with computers an various audio-visual stuff operating on standby).

The last quarter's bills were noticeably higher than the same quarter in
2024.

Post by David
If her bills have gone up significantly after a "free" installation then
that opens a whole can of worms.
Cheers
Dave R

[Brian]

Post by David
I know, I know, piece of string etc.
A distantly related family member has had a "green energy upgrade" free of
charge from the local council.
It consists of solar panels, a hybrid system of air source heat pump and
gas boiler.
She is now struggling to pay the energy bills.
Reportedly £350 a month, but further information being sought.
Also trying to find out what the bills were prior to the "free" upgrade.
We have a (modified) 1930s 3 bed semi with good insulation (especially
after the extension), good solar gain, gas heating and hob, electric
cooker and microwave.
Our annual predicted bill this month is just over £2,500.
Just over £300 for the coldest months of the year, but considerably less
in the summer.
I am thinking that solar panels and an air source heat pump should reduce
overall running costs.
However it is possible that a poor installation would actually increase
annual costs.
In which case the installation would not be appropriate.
I am now asking if anyone has an "average" 1930s 3 bed semi, and if so
what the energy bills look like over the year.
Just for a comparison, to see if the costs in her case are abnormally high.
If her bills have gone up significantly after a "free" installation then
that opens a whole can of worms.
Cheers
Dave R

We have a large, by most people’s standards, 5 bed, 1980s, detached house.
Well insulated, built with cavity wall insulation (polystyrene), condensing
boiler ( must be 15 + years old). Double glazed.

We pay £250 / mth in total (gas & electric) but I expect to be in credit -
we normally are.

That includes charging our hybrid several times / month and, in the winter,
running a small heater in the Motorhome on a thermostat to keep it above 10
C and a dehumidifier.

One tip, several years back I changed our ‘dumb’ heating controller for a
Hive system. The kit cost about £120 and I installed it myself - about an
hour if that.

Using the data from the system, I was able to ‘tweak’ the schedule and,
without any loss in comfort, reduce our gas bill dramatically.

Add in the ability control the system remotely - for example when returning
from a trip I can turn on the heating and/or hot water - and it is a game
changer.